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<blockquote data-quote="keep_hope_alive" data-source="post: 8068208" data-attributes="member: 576029">the point of using an oscilloscope to set gains is to match the output voltage of the head unit with the input sensitivity of the amplifier&#039;s pre-amp section.&nbsp; To do this you will need both the head unit and the amplifier, and obviously cables to connect everything.&nbsp; You will need a source signal, such as a CD with sine waves&nbsp; - 50Hz and 1000Hz are common for subwoofers and speakers, respectively.You play the CD, and measure the outputs of the amplifier.&nbsp; You choose a head unit volume to set the gains with, this is never the max output of the HU, we commonly use 70% or so if the speakers are also amplified externally.&nbsp; If you have speakers powered off your head unit, then you may set gains a lot lower since the head unit will have audible distortion around 50% volume.&nbsp; Once you have chosen the HU volume to use and the test tone track to use (put on repeat) , you adjust amplifier gains until you see clipping then turn back down.&nbsp;&nbsp; Note that you do not connect both scope leads, just the red one. you ground the black lead to chassis/amp ground.&nbsp; if the amp is bridgable you will see that there is a signal on left (+) and right (-) but the right (-) is 180deg out of phase.&nbsp; you can discuss how the concept of bridging works for extra credit.&nbsp; Be prepared to do an Ohm&#039;s law calc to discuss what power output this will be at the expected impedance load.&nbsp; Note that once you connect the load, some voltage sag will happen and the actual power output may decrease.The supply voltage used will determine where the amplifier&#039;s voltage rails are, and thus where you will start to clip.&nbsp; To do this in class you will need a power supply capable of 5A or so between 12VDC-13.8VDC</blockquote>

[QUOTE="keep_hope_alive, post: 8068208, member: 576029"] the point of using an oscilloscope to set gains is to match the output voltage of the head unit with the input sensitivity of the amplifier's pre-amp section. To do this you will need both the head unit and the amplifier, and obviously cables to connect everything. You will need a source signal, such as a CD with sine waves - 50Hz and 1000Hz are common for subwoofers and speakers, respectively. You play the CD, and measure the outputs of the amplifier. You choose a head unit volume to set the gains with, this is never the max output of the HU, we commonly use 70% or so if the speakers are also amplified externally. If you have speakers powered off your head unit, then you may set gains a lot lower since the head unit will have audible distortion around 50% volume. Once you have chosen the HU volume to use and the test tone track to use (put on repeat) , you adjust amplifier gains until you see clipping then turn back down. Note that you do not connect both scope leads, just the red one. you ground the black lead to chassis/amp ground. if the amp is bridgable you will see that there is a signal on left (+) and right (-) but the right (-) is 180deg out of phase. you can discuss how the concept of bridging works for extra credit. Be prepared to do an Ohm's law calc to discuss what power output this will be at the expected impedance load. Note that once you connect the load, some voltage sag will happen and the actual power output may decrease. The supply voltage used will determine where the amplifier's voltage rails are, and thus where you will start to clip. To do this in class you will need a power supply capable of 5A or so between 12VDC-13.8VDC [/QUOTE]

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